KR910005192B1 - Catalytically active silica and alumina gel and process for preparing it - Google Patents

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Description

Catalytically Active Silica and Alumina Gels and Their Processes

Figure 1 shows the spectra of the gels as shown in the I.R. spectroscopic analysis carried out by the FTIR-1730 spectrometer manufactured by Perkin Elmer.

The present invention relates to catalytically active silicas and alumina gels and processes for their preparation.

The present invention also relates to the use of silica and alumina gels as catalysts in hydrocarbon conversion processes. It is known in the art to be used as zeolites in absorption and separation processes of that kind, or as catalysts in various conversions of hydrocarbons. Zeolites, also known as molecular sieves, are alumino-silicates of natural or synthetic origin of crystalline nature. For this known technique, see Kirk-Hautmer's Review of Encyclopaedia of Chemical Technology, 3rd edition, Volume 15, pages 638-669.

It has also been described in the art that certain silica and alumina gels of amorphous nature have catalytic activity. That is, for example, European Patent Application Nos. 160 and 145 are of amorphous nature and normally have pores with diameters in the range of 50 to 500 mm 3, and the ratio of silica to alumina is usually from 1/1 to 10/1. We present an alkalizing process of aromatic hydrocarbons using a catalyst consisting of silica and alumina gel as in the range of. M.R.S Manton and J.C. Davids, in the Journal of Catalysis (60,156-166 (1979)), used silica and alumina to control its pore size using catalysts of pores with diameters normally in the range of 3.7 to 15 mm (37 to 150 microns). A process for synthesizing an amorphous catalyst is presented.

We have found here microporous catalytically active silicas and alumina gels that are amorphous in terms of X-rays and may show unexpectedly high values of selectivity for useful reaction phases in hydrocarbon conversion processes.

Accordingly, the present invention exhibits amorphousness in the X-ray, the molecular ratio of SiO ₂ / Al ₂ O ₃ is in the range of 30/1 to 500/1 and has a surface area in the range of 500 to 100 m ² / g It is related to silica and alumina gel in which the total volume of is in the range of 0.3 to 0.6 ml / g and the average diameter of the pores is less than 10 mm 3 and is separated or substantially separated from the pores with diameters greater than 30 mm. Soluble compounds of aluminum obtainable from Al ₂ O ₃ by hydrolysis using the amount of the solution components in accordance with the molar ratio of are also ethyl, n-propyl and n- of the soluble silicone compounds obtainable from SiO ₂ by hydrolysis. Preparing an (TAA-OH) aqueous solution of tetra-alkyl-ammonium hydroxide with an alkyl group selected from butyl; SiO ₂ / Al ₂ O ₃ 30: 1 to 50: 1; TAA-OH / SiO ₂ 0.05: 1 to 0.2: 1; H ₂ 0 / SiO ₂ 5: 1 to 40: 1; (b) heating the solution to cause gelation; (c) the obtained gel is dried; It can also be obtained by calcining the dried gel, first working in an inert atmosphere and then again in an oxidizing atmosphere.

It is important to use tetra-ethyl-ammonium, tetra-n-propyl-ammonium or tetra-n-butyl-ammonium hydroxide in step (a) of this process. The use of similar ammonium compounds, such as tetra-methyl-ammonium hydroxide, results in silica and alumina gels with medium or small pore sizes (more than 30 microns in pore size) that are not catalytically or less catalytically active.

Preferred soluble aluminum compounds which can be used in step (a) of this process are aluminum trialkoxides, for example aluminum tri-n-propoxide and aluminum tri-isopropoxide.

Preferred soluble silicone compounds which can be used in step (a) of this process are tetraalkyl silicates, for example tetra-ethyl silicate. Step (a) of the process is carried out at room temperature (20-25 ° C.) or at a temperature (about 50 ° C.) until it is close to the value at which gelation above room temperature starts.

The order in which each component of the solution is added in step (a) is not critical. However, it is preferred to first form an aqueous solution containing tetra-alkyl-ammonium hydroxide and soluble aluminum compound together with the soluble silicone compound first, followed by addition of the auxiliary solution.

In any case, the molar ratio of the resulting solution is -SiO ₂ / Al ₂ O ₃ 30: 1 to 500: 1; -TAA-OH / SiO ₂ 0.05: 1 to 0.2: 1; -H ₂ O SiO ₂ 5: 1 to 40: 1 and preferred molar ratios are: -SiO ₂ / Al ₂ O ₃ 50: 1 to 300: 1; -TAA-OH / SiO ₂ 0.05: 1 to 0.1: 1; -H ₂ O / SiO ₂ 10: 1 to 25: 1.

In step (b) of the present process, gelation is carried out by heating the solution at a level of 50 ° C to 70 ° C, preferably 60 ° C. The gel completion time is a function of temperature, concentration or other parameter (variable) and therefore varies and usually consists of a range of 15 to 5 hours and normally within 25 to 60 minutes. It is important that the gelation work is done by simple solution heating means.

Working in acidic conditions, as is known, leads to silica and alumina gels, which have unnecessary properties, particularly in porosity and size distribution of pores.

The gel is sent to step (c) of the process according to the invention and dried. The drying operation is carried out at a temperature of up to about 150 ° C., preferably at a temperature of 90-100 ° C., for a sufficient time to completely or substantially completely remove the moisture.

According to a practical embodiment of the invention, the drying operation of step (c) is spray-drying. In this case the gel is injected in the form of droplets in contact with an inert gas operated at an inlet temperature of 230-250 ° C. and an outlet temperature of 140-160 ° C. in the spray-dryer used.

In any case, the dried gel enters the calcination process, step (d) of the present invention, which is first performed suitably first in an inert atmosphere, ie in nitrogen and then in an oxidizing atmosphere like air. Calcination temperature is suitable in the range of 500 to 700 ℃ preferably 550-600 ℃.

Calcification time varies from 4 to 20 hours and is normally 6-16 hours. Thus in accordance with the invention SiO ₂ / Al in the range of 30: 1 to 500: 1 and preferably 50: 1 to 300: 1, which is a value similar to that derived from the fully amorphous structure and initially introduced silicon and aluminum compounds on X-rays. Silica and alumina gels having a ratio of ₂ O ₃ are obtained.

The silica and alumina gels have a large surface area with specific surface area values ranging from 500 to 1000 m ² / g (BET measurement). The total volume of pores is 0.3 to 0.6 ml / g. The pore size is in the micropore range with an average diameter of less than 10 mm 3 and a narrow size distribution. In particular, there are no pores with a diameter of 30 mm 3 or more and generally no pores with a diameter of 20 mm 3 or more.

Silicas and alumina gels according to the invention are catalytically active in hydrocarbon conversion processes. Such materials can be used in combination with a suitable metal oxide that acts as a blinding agent. Suitable oxides used herein include silica, alumina and titanium, magnesium and zirconium oxides. The silica and alumina gel and the binder may be mixed in a weight ratio in the range of 50:50 to 95: 5, preferably 70:30 to 90:10. These two components can be mixed by means of traditional mixing techniques and the resulting mixture can be made in the required form, such as in extruded or in the form of particles. This work improves the mechanical properties of the catalyst.

Catalytic reaction with silica-alumina gel according to the present invention includes the dimerization of olefins, in particular the dimerization of linear olefins of 4 to 15 carbon atoms and the isomerization of butanebutene and alkylation of hydrocarbons with olefins. There is also a dewaxing reaction. In this reaction the catalyst of the present invention shows high activity and above all high selectivity for useful reaction products.

The following experimental examples are presented to better illustrate the present invention.

Example 1

To 50 g of 30.6 wt% tetra-n-propyl-ammonium hydroxide (TPA-OH) is dissolved 1.4 g of aluminum tripropoxide [Al (OnC ₃ H ₇ ) ₃ ] and 56 g of demineralized water is added. This operation is carried out at room temperature (about 20 ° C.). The solution obtained here is heated to 60 ° C. and then stirred with the addition of 104 g of tetra-ethyl-silicate (TES).

The molar ratio of the mixture obtained here is as follows: -SiO ₂ / Al ₂ O ₃ = 145: 1; -TPA-OH / SiO ₂ = 0.15: 1; -H ₂ O / SiO ₂ = 10: 1.

The mixture is stirred at 60 ° C. and 30 minutes afterwards to obtain a uniform gel dried under airflow conditions in an oven at 100 ° C. in a rotary evaporator with a water temperature controlled bath to maintain 90 ° C.

The dried gel is calcified at 600 ° C. for 3 hours under nitrogen flow conditions and then again for 10 hours under air flow conditions. 30 g of silica-alumina gel is obtained with respect to the amount of silicon and aluminum initially charged.

The chemical analysis can confirm that the reaction mixture after the addition of the reactant in the molar ratio of SiO ₂ / Al ₂ O ₃ . X-ray diffraction of the powder confirms the completely amorphous properties of silica and alumina gel with a vertical Philips goniometer using Cuk α radiation.

The surface area of the gel measured at Sorptomatic 1800 of Carlo Erva was 800 m ² / g. There are no pores with a diameter of 20 mm 3 or more, and the porosity of the gel having an average diameter of 10 mm pore is 0.44 ml / g.

Both of these measurements are carried out with the Sophromatic 1800 from Carlo Erva.

Example 2

2 g of aluminum tripropoxide is added to 27 g of 30 wt% TPA-OH, dissolved, and 85 g of demineralized water is added.

The solution obtained here is heated from 20 ° C. to 60 ° C. and 104 g of TES is added.

The molar ratio of the mixture obtained here is as follows: -SiO ₂ / Al ₂ O ₃ = 102; -TPA-OH / SiO ₂ = 0.08; -H ₂ O / SiO ₂ = 11.5

The mixture is stirred at 60 ° C. until a clear and dense gel is obtained (the time required is about 30 minutes) and the gel is first stirred in a rotavapor and then in an oven at 100 ° C. for 1 hour. To dry.

The calcification is carried out at 550 ° C. for 1 hour under nitrogen flow conditions and then for 5 hours under air flow conditions again.

27 g of silica-alumina gel having a molar ratio of SiO ₂ / Al ₂ O ₃ as described above and completely amorphous on the X-rays was obtained. The gel has a surface area of 658 m ² / g porosity of 0.46 ml / g and no pores with a diameter of 20 μs or more, and an average diameter of pore of 10 μs or less.

Example 3

A clear solution of 2 g of aluminum-tri-propoxide dissolved in 40.5 g of 25 wt% TPA-OH at room temperature (about 20 ° C.) is added to 146 g of demineralized water.

The solution is heated to 60 ° C. and then 104 g of TES is added thereto. The molar ratio of the mixture obtained here is as follows: -SiO ₂ / Al ₂ O ₃ = 102; -TPA-OH / SiO ₂ = 0.10; -H ₂ O / SiO ₂ = 21.

The mixture is stirred at 60 ° C. for about 1 hour until a uniform gel is obtained. The gel is allowed to stand at room temperature (about 20 ° C.) for 50 hours and then dried under atmospheric pressure and small airflow conditions in a rotary evaporator with a temperature controlled bath to maintain 90 ° C. Finally, the gel is dried at 150 ° C. for 1 hour and then calcined at 550 ° C. for 3 hours under nitrogen flow conditions and 13 hours at 600 ° C. under air flow conditions.

By 30 g of silica-alumina gel having a molar ratio of SiO ₂ / Al ₂ O ₃ as described above and completely amorphous on X-rays was obtained. The gel has a surface area of 760 m ² / g porosity of 0.44 ml / g and does not contain pores with a diameter of 20 μs or more, and average pore size of 10 μs or less.

Example 4

2 g of aluminum-tri-propoxide is dissolved in 51 g of 30 wt% TPA-OH at room temperature (about 20 ° C.) and 180.0 g of demineralized water is added thereto.

The solution is heated to 60 ° C. and then 104.2 g of TES is added thereto. The molar ratio of the mixture obtained here is as follows: -SiO ₂ / Al ₂ O ₃ = 102; -TPA-OH / SiO ₂ = 0.15; -H ₂ O / SiO ₂ = 24.

The mixture was stirred at 60 ° C. for 4 hours and left at room temperature (about 20 ° C.) for 11 days, then sprayed the mixture at a flow rate of 4.5 ml / min in a dryer with gas inlet temperature of 240 ° C. and outlet temperature of 150 ° C. -Dry it. The dried gel is calcified at 550 ° C. for 1 hour under nitrogen flow conditions and 5 hours under air flow conditions.

Completely amorphous silica in a molar ratio of the linear X- SiO ₂ / Al ₂ O ₃ is equal to the above-obtained aluminum gel by 29g. The gel has a surface area of 541 m ² / g, porosity of 0.47 mg / g, and does not include pores with a diameter of 20 mm 3 or more, and the average diameter of pores is 10 mm 3 or less.

Example 5

0.68 g of aluminum-tri-propoxide was dissolved in 50 g of 30.6 wt% TPA-OH at room temperature (approximately 20 ° C.), 56 g of demineralized water was added thereto, heated to 50 ° C., and 104 g of TES Add.

The molar ratio of the mixture obtained here is as follows: -SiO ₂ / Al ₂ O ₃ = 300; -TPA-OH / SiO ₂ = 0.15; -H ₂ O / SiO ₂ = 10.

The mixture is stirred at 50 ° C. for 1.5 hours until a clear, dense gel is obtained, first drying for 3 hours in a rotary evaporator first temperature-controlled to 80 ° C. and then for 1 hour in an oven at 120 ° C.

Finally, the dried gel is calcified at 600 ° C. for 3 hours under nitrogen flow conditions and 7 hours under air flow conditions.

30 g of a silica-aluminum gel having the same molar ratio of SiO ₂ / Al ₂ O ₃ as described above and completely amorphous on X-rays is obtained. The gel has a surface area of 974 m ² / g porosity of 0.45 ml / g and is free from pores with a diameter of 20 μs or more, and the average diameter of pores is 10 μs or less.

Example 6

4 g of aluminum-tri-propoxide was dissolved in 48.5 g of 25 wt% TPA-OH at room temperature (about 20 ° C.), and 170 g of water was added thereto, heated to 60 ° C., and 104 g of TES was added thereto. Add.

The molar ratio of the mixture obtained here is as follows: -SiO ₂ / Al ₂ O ₃ = 51; -TPA-OH / SiO ₂ = 0.12; -H ₂ O / SiO ₂ = 23.

The mixture was stirred at 60 ° C. for 25 minutes and allowed to stand at room temperature for 10 hours until a clear, dense gel was obtained and then dried under air flow conditions for 3 hours in a rotary evaporator with a water temperature controlled bath to maintain 90 ° C. And dried in an oven at 100 ° C.

Finally, the dried gel is calcified at 600 ° C. for 3 hours under nitrogen flow conditions and 13 hours under air flow conditions.

28 g of a silica-aluminum gel having a molar ratio of SiO ₂ / Al ₂ O ₃ as described above and having a surface area of 810 m ² / g is obtained. The gel has a porosity of 0.44 ml / g and no pores with a diameter of more than 20 mm 3, and the average diameter of pores is less than 10 mm 3.

Example 7 (comparative example)

This process is carried out in the same manner as in Example 1 using tetramethyl-ammonium hydroxide (TMA-OH) instead of TPA-OH.

The molar ratio of the mixture after TES addition is as follows: -SiO ₂ / Al ₂ O ₃ = 145; -TMA-OH / SiO ₂ = 0.15; -H ₂ O / SiO ₂ = 10.

As much as 29 g of a silica-alumina gel having a molar ratio of SiO ₂ / Al ₂ O ₃ as described above and completely amorphous on X-rays is obtained. The gel has a surface area of 231 m ² / g porosity of 0.44 ml / g and an average diameter of pores in the range of 10 kPa to 100 kPa.

Example 8

This process is carried out in the same manner as in Example 1 using tetra-ethyl-ammonium hydroxide (TEA-OH) instead of TPA-OH.

The molar ratio of the mixture after TES addition is as follows: -SiO ₂ / Al ₂ O ₃ = 145; -TEA-OH / SiO ₂ = 0.15; -H ₂ O / SiO ₂ = 10.

A silica-alumina gel is obtained in an amount corresponding to the molar ratio of SiO ₂ / Al ₂ O ₃ as described above, which is completely amorphous on X-ray, has a surface area of 539 m ² / g and a porosity of 0.40 ml / g. Has a value. There are no pores with a diameter of 30 mm 3 or more in the gel, and the size of pores is 10 mm 3 or less.

Example 9

This process is carried out in the same manner as in Example 1 using tetra-butyl-ammonium hydroxide (TBA-OH) instead of TPA-OH.

The molar ratio of the mixture after TES addition is as follows: -SiO ₂ / Al ₂ O ₃ = 145; -TBA-OH / SiO ₂ = 0.15; -H ₂ O / SiO ₂ = 10.

By 30 g of silica-alumina gel having a molar ratio of SiO ₂ / Al ₂ O ₃ as described above and completely amorphous on X-rays was obtained. The gel has a surface area of 929 m ² / g porosity of 0.45 ml / g and no pores with a diameter of 20 μs or more, and an average diameter of pores of 10 μs or less.

Example 10

Previously purified by distillation through a 20-tray distillation column: (a) linear isomeric mixture of tetradecane; (b) 7-tetradecane (Aldrich); purity 98%); (c) 1-octane, some of silica and alumina gels prepared from the above examples are used as catalysts for the dimerization of linear olefins selected from among the above examples. Specifically, the dimer polymerization test is performed according to the following method. 0.2-0.4 g of catalyst and 6 ml of olefin are placed in a small autoclave of pyrex glass. The mixture is heated and stirred at the desired temperature using a temperature controlled bath. At the end of the reaction time, the reaction product is analyzed by quantitative gas-chromatographic analysis. The properties of this product are confirmed by mass spectrometry. Table 1 shows the reaction conditions together with the yield of dimers and trimers. The remainder of the percentage is a linear isomer of the olefin starting material.

TABLE 1

Claims (14)

The molar ratio of SiO ₂ / Al ₂ O ₃ in the range of 30/1 to 500/1 and the surface area in the range of 500 to 1,000 m ² / g and the total volume of pores in the range of 0.3 to 0.6 ml / g and It has pores of average diameter size of less than 10 mm 3 and no pores of diameter size greater than 30 mm 3; (a) using a solution component according to the following molar ratio: SiO ₂ / Al ₂ O ₃ 30: 1 to 500: 1; TAA-OH / SiO ₂ 0.05: 1 to 0.2: 1; H ₂ O / SiO ₂ 5: 1 to 40: 1; Tetra-alkyl-ammonium hydroxides with alkyl groups selected from ethyl, n-propyl and n-butyl of soluble compounds of aluminum obtainable from Al ₂ O ₃ by hydrolysis and of soluble silicon compounds obtainable from SiO ₂ by hydrolysis Making an aqueous solution of lockside (TAA-OH); (b) heating the solution to cause gelation; (c) the gel obtained is dried; And (d) silica and alumina gel obtained by first calcifying the dried gel first under inert atmosphere and then again under oxidative atmosphere. The silica and alumina gel of claim 1, wherein the soluble compound of step (a) is aluminum tri-alkoxide and the soluble silicone compound of step (a) is tetra-alkyl silicate. The silica and alumina gel according to claim 2, wherein the soluble aluminum compound is aluminum tri-n-propoxide or aluminum tri-isopropoxide and the soluble silicon compound is tetra-ethyl silicate. 2. The silica and alumina gel according to claim 1, wherein the solution component of step (a) is present in an amount consisting of the following molar ratios: -SiO ₂ / Al ₂ O ₃ 50: 1 to 300: 1; -TAA-OH / SiO ₂ 0.05: 1 to 0.2: 1; -H ₂ O / SiO ₂ 10: 1 to 25: 1. The silica and alumina gel of claim 1, wherein the reaction of step (a) takes place in a range from room temperature (20-25 ° C.) to gelation start temperature (about 50 ° C.). The silica and alumina gel according to claim 1, wherein the gelling reaction of step (b) is performed for a time within a range of 15 minutes to 5 hours in a temperature range of 50 ° C to 70 ° C. The silica and alumina gel according to claim 6, wherein the gelation reaction is carried out at a temperature of 60 DEG C for about 25 to 60 minutes. The silica and alumina gel of claim 1, wherein (c) the drying step is carried out to a temperature of up to 150 ° C. The silica alumina gel according to claim 8, wherein the drying step (c) is performed at a temperature of about 90-100 ° C. The silica and alumina gel according to claim 1, wherein the drying step (c) is performed by spray-drying. The silica and alumina gel of claim 1, wherein (d) the calcification step is carried out for 4 to 20 hours at a temperature in the range of 500 ° C to 700 ° C. 12. The silica and alumina gel of claim 11, wherein said (d) calcification step is performed at a temperature of about 550-600 [deg.] C. for about 6-16 hours. Use of the silica according to claims 1 to 12 in the catalytic process of hydrocarbon conversion. The method of claim 13, wherein the catalytic process is a dimer polymerization process of straight olefins containing 4 to 15 carbon atoms in a molecule.

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